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Nguyen, Dat Xuan, Vu Hoang Nguyen, and Phuong Xuan Pham. "DEVELOPING AND VALIDATING A GT-SUITE BASED MODEL FOR A SECOND GENERATION COMMONRAIL SOLENOID INJECTOR." Vietnam Journal of Science and Technology 59, no. 3 (May 17, 2021): 390. http://dx.doi.org/10.15625/2525-2518/59/3/15803.
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Injection profiles, containing important parameters like injection rate, directly affect the spray structure, fuel-air mixture quality, and as such the physical and chemical processes occurring in the IC engine’s combustion chamber. Therefore, injection profiles are one of the keys to improving power, thermal efficiency and minimizing the emission for IC engines. In this paper, a GT-Suite - based simulation model for a second generation solenoid commonrail injector typically utilized in Hyundai 2.5 TCI-A diesel engines, has been successfully developed and validated. The validation is done by using experimental data are acquired by a Zeuch’s method-based Injection Analyzer (UniPg STS) in University of Perugia, Italy. The calibration data is measured over a wide range of rail pressure and energizing time (ET) corresponding to the engine operating conditions. The results show that the injector model developed here is reliable and suitable for examining the injector’s hydraulic characteristics. The difference in start of injection values obtained through experiment and simulation is only about 15 µs. The total injection volumes obtained through experiment and simulation under ET > 0.8 ms is less than 10 % while the difference is quite high under ET < 0.8 ms and high rail pressure (up to 34.5 %).
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Brighenti, Attilio, Davide Duranti, and Debora Quintabà. "TGSim Plus™—Real-Time Dynamic Simulation Suite of Gas Turbine Systems for the MATLAB®/Simulink® Environment." International Journal of Turbomachinery, Propulsion and Power 5, no. 3 (September 11, 2020): 24. http://dx.doi.org/10.3390/ijtpp5030024.
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Dynamic simulation of turbomachinery by Hardware in the Loop (HIL) real-time systems has become an essential practice, due to the high cost of real equipment testing and the need to verify the control and diagnostic systems’ reaction to emergency situations. The authors developed a full model of a power generation Gas Turbine Plant, including liquid and gaseous auxiliaries, and the electrical generator and starter motor, integrated in a MATLAB®/Simulink® simulation suite: TGSim Plus™. This allows assembling models of various gas turbine (GT) architectures by customised Simulink® library blocks and simulating steady state and transient conditions, such as complete start-up and shutdown operations as well as emergency, contingent operations and artificially injected fault scenarios. The model solver runs real-time steps at milliseconds scale. The paper describes the main modelling characteristics and typical results of steady state and transient simulations of a heavy-duty gas turbine under development by Doosan Heavy Industries and Construction (Changwon, South Korea). Comparison with benchmark design simulations obtained by a reference non real-time software shows a good match between the two environments, duly taking into account some differences in the GT models setting affecting parts of the sequence. The paper discusses also the bleed streams warm-up influence on GT performance and the start-up states trajectories dependency on control logic and on the starter helper motor torque envelope.
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Kin, Taichi, Hiroshi Oyama, Masaaki Shojima, Masahiro Shin, and Nobuhito Saito. "Three-dimensional Fusion Imaging and Virtual Operative Simulation(Operation Suite in 21st Century)." Japanese Journal of Neurosurgery 20, no. 4 (2011): 238–46. http://dx.doi.org/10.7887/jcns.20.238.
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Irfan, Muhammad, Viktor Berbyuk, and Håkan Johansson. "Minimizing synchronization time of a gear shifting mechanism by optimizing its structural design parameters." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 2-3 (July 10, 2019): 488–504. http://dx.doi.org/10.1177/0954407019860363.
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A gear shifting mechanism is modeled in GT-Suite software. The mechanism has three main bodies: sleeve, ring, and gear. Results obtained from the simulation show that GT-Suite model can predict gear shifting process. Synchronization processes for three conditions of nominal, road grade, and vibrational motion of the master are studied in six cases by considering the sleeve and the gear as a master alternatively. The optimization based on the GT-Suite model is performed for each case to find the minimum gear shifting time based on variations of 17 structural design parameters. Minimum synchronization time is found almost same in all cases. It is concluded from closeness of the optimization results that average of the parameter values can be considered as optimized values for all cases. At the end, robustness of the optimized structural design parameters are analyzed with respect to the road grade, amplitude, and frequency of oscillatory excitation of rotational motion of the master.
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Adsul, Pranita, Vinod Kotebavi, Sanjeev Bedekar, and Ashwini Mishra. "A Simulation study of cooling system for heavy duty diesel engine." MATEC Web of Conferences 172 (2018): 02002. http://dx.doi.org/10.1051/matecconf/201817202002.
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The main function of the cooling system is to control the temperature of the engine components and improve the performance of an engine. To know the flow and temperature distribution in the jacket cooling system for 6 cylinder diesel engine is analyzed using 1 dimensional method by using GT-Suite 1D simulation software package. The present work employs 1D simulation of water jacket in GT-ISE to perform a comprehensive study of mass-flow and thermal distribution over the inlet of the cooling package of a selected engine in several steady state operating points. The results show, that the suggested predictive method successfully captures the thermal effect of recirculation while reducing the necessity for calibration done by prototype testing.
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Petersen, Nadine Felicity. "Childhood education student teachers responses to a simulation game on food security." South African Journal of Childhood Education 4, no. 1 (July 1, 2014): 16. http://dx.doi.org/10.4102/sajce.v4i1.116.
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<p><em>This paper provides an account of student teachers responses to a simulation game about food scarcity and how the game served as a conversation starter about the influence of food scarcity on educational provisioning. The simulation game was utilised as part of a suite of activities during an educational excursion for first years in primary school teacher education. In this investigation data were generated via </em><em>video recordings of the simulation game itself, summary notes of the key points of the discussion session during the game, and students’ learning portfolios. Analysis </em><em>of the various data sets indicate that student-teachers’ engaged with the game both viscerally and cerebrally, with the game </em><em>providing a powerful concrete introduction to the issues of food scarcity and unequal distribution of resources. Most student teachers were able to relate the lessons learned from the game to the classroom and educational situation. </em><em>In addition, I found that the simulation game as method can assist students in their activity of learning to look at education as an equity and justice issue.</em><strong><em> </em></strong></p>
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Li, Ming Hai, Feng Jiang, Biao Liu, and Ming Gao Ouyang. "Simulation Research on Post-Injection of Electronically Controlled Heavy-Duty Diesel Engine." Applied Mechanics and Materials 121-126 (October 2011): 2238–42. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.2238.
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GT-Suite software is used to establish the simulation model of electronic fuel injection system for 16V280ZJ diesel engine. Combustion process simulation calculation is conducted to the direct injection (DI) diesel engine based on a main-post double injection scheme. Simulation parameters are modified based on the comparison with given experimental results. The calculation results effectively reflect the influence of fuel ratio and the interval angle between main and post injection over emission and fuel economy. Finally, in order to improve the engine emissions and reduce the pressure rise rate, we get the optimal injection solution for the main-post injection mode.
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Li, Ming Hai, Biao Liu, and You Bo Ning. "Analysis on Effects of Fuel Cam on High-Pressure Fuel System." Advanced Materials Research 328-330 (September 2011): 948–52. http://dx.doi.org/10.4028/www.scientific.net/amr.328-330.948.
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GT-Suite software is used to establish the simulation model of high-pressure fuel injection system for diesel engine. Simulation parameters are modified based on the comparison with given experimental results. In order to improve diesel engine fuel injection performance, the cam profile was improved to ensure a high injection pressure and smooth operating characteristics. A more reasonable fuel cam profile was designed by analyzing the injection characteristics and dynamics. It improves the fuel mixture formation and combustion, so diesel economy and emissions performance are also guaranteed.
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Tian, Feng, Guo Feng Ren, Bin Yan, Guo Qiang Ao, and Lin Yang. "Optimization of Hybrid Turbocharger Applied on Common Rail Diesel Engine with Exhaust Gas Recirculation." Applied Mechanics and Materials 246-247 (December 2012): 84–88. http://dx.doi.org/10.4028/www.scientific.net/amm.246-247.84.
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Turbocharger is an effective technique to achieve higher thermal efficiency reduced emissions. And hybrid turbocharger is proven to be a promising technique to eliminate the well-known 'turbo-lag' effect of the turbocharger. In this paper, a global optimization of hybrid turbocharger technique with variable geometry turbine and exhaust gas recirculation was carried out. The diesel engine was modeled by GT-SUITE software, which is a 1D simulation environment. Moreover, a dynamic programming based optimizer, which was developed in Simulink, was integrated with the diesel engine model. Simulations results show that the optimized parameters can improve the engine fuel economy significantly under Chinese typical urban driving cycle.
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Huertas-Company, Marc, Vicente Rodriguez-Gomez, Dylan Nelson, Annalisa Pillepich, Connor Bottrell, Mariangela Bernardi, Helena Domínguez-Sánchez, et al. "The Hubble Sequence at z ∼ 0 in the IllustrisTNG simulation with deep learning." Monthly Notices of the Royal Astronomical Society 489, no. 2 (August 30, 2019): 1859–79. http://dx.doi.org/10.1093/mnras/stz2191.
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ABSTRACT We analyse the optical morphologies of galaxies in the IllustrisTNG simulation at z ∼ 0 with a convolutional neural network trained on visual morphologies in the Sloan Digital Sky Survey. We generate mock SDSS images of a mass complete sample of $\sim 12\, 000$ galaxies in the simulation using the radiative transfer code SKIRT and include PSF and noise to match the SDSS r-band properties. The images are then processed through the exact same neural network used to estimate SDSS morphologies to classify simulated galaxies in four morphological classes (E, S0/a, Sab, Scd). The CNN model classifies simulated galaxies in one of the four main classes with the same uncertainty as for observed galaxies. The mass–size relations of the simulated galaxies divided by morphological type also reproduce well the slope and the normalization of observed relations which confirms a reasonable diversity of optical morphologies in the TNG suite. However we find a weak correlation between optical morphology and Sersic index in the TNG suite as opposed to SDSS which might require further investigation. The stellar mass functions (SMFs) decomposed into different morphologies still show some discrepancies with observations especially at the high-mass end. We find an overabundance of late-type galaxies ($\sim 50{{\ \rm per\ cent}}$ versus $\sim 20{{\ \rm per\ cent}}$) at the high-mass end [log(M*/M⊙) > 11] of the SMF as compared to observations according to the CNN classifications and a lack of S0 galaxies ($\sim 20{{\ \rm per\ cent}}$ versus $\sim 40{{\ \rm per\ cent}}$) at intermediate masses. This work highlights the importance of detailed comparisons between observations and simulations in comparable conditions.
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Atia, Doaa M., and Hanaa T. El-madany. "VHDL Based Maximum Power Point Tracking of Photovoltaic Using Fuzzy Logic Control." International Journal of Electrical and Computer Engineering (IJECE) 7, no. 6 (December 1, 2017): 3454. http://dx.doi.org/10.11591/ijece.v7i6.pp3454-3466.
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It is important to have an efficient maximum power point tracking (MPPT) technique to increase the<em> </em>photovoltaic (PV) generation system output efficiency. This paper presents a design of MPPT techniques for<em> </em>PV module to increase its efficiency. Perturb and Observe method (P&O), incremental conductance method (IC), and Fuzzy logic controller (FLC) techniques are designed to be used for MPPT. Also FLC is built using<em> </em>MATLAB/ SIMULINK and compared with the FLC toolbox existed in the MATLAB library. FLC does not<em> </em>need knowledge of the exact model of the system so it is easy to implement. A comparison between different<em> </em>techniques shows the effectiveness of the fuzzy logic controller techniques. Finally, the proposed FLC is<em> </em>built in very high speed integrated circuit description language (VHDL). The simulation results obtained with<em> </em>ISE Design Suite 14.6 software show a satisfactory performance with a good agreement compared to obtained values from MATLAB/SIMULINK. The good tracking efficiency and rapid response to environmental parameters changes are adopted by the simulation results.
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Daya, Rohil, John Hoard, Sreedhar Chanda, and Maneet Singh. "Insulated catalyst with heat storage for real-world vehicle emissions reduction." International Journal of Engine Research 18, no. 9 (January 8, 2017): 886–99. http://dx.doi.org/10.1177/1468087416685470.
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In previous publications, the model development and simulation of a vacuum-insulated catalytic converter was presented. GT-Suite model simulations demonstrated the heat retention capacity of the converter and corresponding emissions reductions. This article provides an update of the converter model development and analysis of real-world benefits of the converter. The vehicle-aftertreatment model of the vacuum-insulated catalytic converter was improved significantly, and detailed explanations of all theoretical modeling considerations are presented. In the absence of experimental data, a flow test experiment was conducted to measure the flow rate in exhaust tailpipe during vehicle soak due to thermosiphon. These results were used as inputs in the GT-Suite model simulations of conventional and hybrid electric vehicles. New model simulations demonstrated the ability of the vacuum-insulated catalytic converter to achieve significant emissions reductions following vehicle soaks of up to 18 h. To examine the real-world benefits of the converter, driving data were obtained from the National Renewable Energy Laboratory, and a MATLAB code was developed to statistically analyze 23,156 drive cycles. The vacuum-insulated catalytic converter was simulated on standard drive cycles to develop a correlation between melt time of the phase-change material and average drive cycle speed and acceleration. This correlation was used to predict the probability that the phase-change material will melt in a given real-world driving cycle. The MATLAB code was also used to calculate the soak time and re-solidification time probability. Finally, Federal Test Procedure emission results were weighted with the soak time probabilities. This analysis showed that in real-world driving conditions, the vacuum-insulated catalytic converter is expected to reduce cold-start CO and hydrocarbon emissions by 26% and 48%, respectively.
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Zeng, Cheng, Dong Bo Yang, Li Liu, and Feng Tian Cai. "Modeling and Simulation Research on the Effect of Driving Skills on Vehicle Fuel Efficiency." Advanced Materials Research 512-515 (May 2012): 1167–73. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.1167.
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The research and application of eco-driving has the important practical significance for the energy conservation and emission reduction of automobile industry. In this paper, a simulation model has been set up based on GT-Suite and mathematical models of driving operations to simulate three typical driving operations. The results show that the acceleration speed plays important role in the acceleration operation. As the acceleration speed increases, fuel economy significantly deteriorates. In the transmission operation, the engine should not be operated in the high speed region. Otherwise, the fuel economy would deteriorate. In the cruise operation, the gear should be selected to matching the speed. High-gear low speed operation will cause safety problems, while low-gear high-speed operation will cause significantly deterioration of fuel economy.
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Y. Yousef, Ayman, and M. H. Mostafa. "Simulation and Implementation of Multiple Unipolar Stepper Motor Position Control in the Three Stepping Modes using Microcontroller." Indonesian Journal of Electrical Engineering and Computer Science 4, no. 1 (November 4, 2016): 29. http://dx.doi.org/10.11591/ijeecs.v4.i1.pp29-40.
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<p>This paper presents a multiple unipolar stepper motor position control system using microcontroller (MCU) in anticlockwise and clockwise directions. The open loop controller of the implemented position control system for the three stepping modes of operation has been designed and developed with three stepper motors and without position feedback. The MCU is programmed using flowcode software package to generate the pulse signals with the desired stepping sequences and step angles. These pulse signals are necessary to drive the three stepper motors in the three drive modes (wave-step, full-step, and Half-step) according to the control algorithm. Three devices of 8 Channel Darlington Driver (chip ULN2803) are used to drive the three stepper motors and provide them with the sufficient current. The position control system has been simulated using proteus design suite software package and the controller has been implemented using low cost PIC16F877A (MCU). A reliable and accurate position control of the stepper motor is achieved by this position control system. </p>
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Abdul Jalal, Rifqi Irzuan, M. A. Mohd Yusoff, H. M. Abid Hasan, and M. N. Yahya. "Simulation of bypass electric water pump to reduce the engine warm-up time." Journal of Mechanical Engineering and Sciences 15, no. 3 (September 19, 2021): 8241–52. http://dx.doi.org/10.15282/jmes.15.3.2021.03.0647.
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There are several strategies have been developed in the automotive cooling system to improve engine thermal management. Basically, these designs use controllable actuators and mechatronic components such as electric water pump, controllable thermostat, and controllable electric fan to improve engine temperature control on most operating ranges. Most of the strategies are complicated and costly. This paper introduced a different approach to improve coolant temperature warm-up during cold start. The new strategy was by promoting a higher coolant flow rate inside the engine block by just installing an electric water pump in the bypass hose. The new approach’s cold start performance was studied using GT-SUITE on a transient model, complete with finite-element of engine block design, lubrication system, components friction model, engine with combustion model and vehicle system. The proposed strategy clearly showed faster coolant temperature increase (18 seconds faster compared to the conventional cooling system). The strategy not only increase the coolant temperature faster, but also increases the oil temperature faster, lower Friction Mean Effective Pressure (FMEP), and lower fuel consumption at certain condition during the warm-up period.
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Reddy, N. Ramanjaneya, Chenna Reddy Pakanati, and M. Padmavathamma. "An Enhanced Queue Management Scheme for Eradicating Congestion of TFRC over Wired Environment." International Journal of Electrical and Computer Engineering (IJECE) 7, no. 3 (June 1, 2017): 1347. http://dx.doi.org/10.11591/ijece.v7i3.pp1347-1354.
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<p class="Abstract">To accomplish increasing real time requirements, user applications have to send different kinds of data with different speeds over the internet. To effectuate the aims of the computer networks, several protocols have been added to TCP/IP protocol suite. Transport layer has to implement emerging techniques to transfer huge amount of data like multimedia streaming. To transmit multimedia applications, one of the suitable congestion control mechanisms in transport layer is TCP Friendly Rate Control Protocol (TFRC). It controls congestion based on its equation. To get more smoothed throughput, intermediate nodes (like Routers. etc.) have to use suitable procedures in all real time situations. To eradicate the level of congestion in the network, we introduce enhanced Holt-Winters equations to RED queue management algorithm and applied to TFRC. The simulation results have shown that this strategy reduces packet loss and increases throughput.</p>
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Menacer, Brahim, Naima Khatir, Mostefa Bouchetara, Ahmed Amine Larbi, and Cherif Belhout. "The Heat Transfer Study in the Diesel Engine Combustion Chamber Using a Two-Zone Combustion Model." Mathematical Modelling of Engineering Problems 7, no. 4 (December 18, 2020): 614–20. http://dx.doi.org/10.18280/mmep.070414.
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The study of heat transfer phenomena in diesel engines is a very complex task considering the number of engine components such as intake and exhaust manifolds, lubricant oil and coolant subsystems, the different heat transfer mechanisms (conduction, convection, and radiation). This paper presents simulation results using a dual-zone model associated to GT-Suite simulation software for the calculation of convective heat transfer from gas to the cylinder wall, radiation heat transfer, gas pressure and temperature for low, partial and full load engine as a function of crank angle for a single-cylinder diesel engine. In this present article, a numerical simulation model was created to foresee the main combustion characteristics, and the simulated results were approved through the reference experiment data. Simulation results showed that any increase in the mass of fuel injected into the combustion chamber would generate a significant increase in the level of pressure and temperature of the combustion gases in the cylinder. This means that despite the improved power performance, excessive fuel consumption would have a negative effect on the thermal behavior and consequently on the life of the engine. The essential objective of any combustion engine development is to reduce fuel consumption while maintaining or improving the engine's power output.
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Xia, Meng, and Fujun Zhang. "Application of Multi-Parameter Fuzzy Optimization to Enhance Performance of a Regulated Two-Stage Turbocharged Diesel Engine Operating at High Altitude." Energies 13, no. 17 (August 19, 2020): 4278. http://dx.doi.org/10.3390/en13174278.
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Air intake and fuel supply conditions are the major factors that affect diesel engine performance at plateau. In a regulated two-stage turbocharged diesel engine, these parameters are reflected as the adjustment of fuel injection mass (mfuel), fuel injection advance angle, and bypass valve opening of a high-pressure stage (HP) turbine. Due to the strongly nonlinear nature and complexity of the diesel engine, it is difficult to find the proper parameter combinations. That is why a model-based optimization method is adopted in this paper. The simulation model of a six-cylinder two-stage turbocharged diesel engine is built on the GT-SUITE platform. According to the analysis of diesel engine operation characteristics at high altitude, a fuzzy optimization algorithm is proposed based on a fuzzy logic controller and is realized in a MATLAB/simulink (MATLAB 2014, Mathworks, Natick, MA, USA) environment. Joint optimization of air intake and fuel supply parameters is then performed on the GT-MATLAB co-simulation platform. Results show that engine torque at full load is significantly increased. At the full load point of 2100 r/min, engine power is increased from 256.5 to 319.6 kW, and brake specific fuel consumption (BSFC) is reduced from 243.1 to 222.3 g/(kW·h). Peak torque is increased from 1944.8 to 2173.2 N·m.
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Funk, Tatiana Andreevna, Yuriy Semenovich Usynin, and Evgeniy Viktorovich Belousov. "Indirect Pulse-vector Control of Wound Rotor Induction Motor Drive in ANSYS Electromagnetics Suite." International Journal of Power Electronics and Drive Systems (IJPEDS) 8, no. 3 (September 1, 2017): 1147. http://dx.doi.org/10.11591/ijpeds.v8.i3.pp1147-1159.
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<span lang="EN-US">This paper deals with the problem of estimation of rotor angular position for the indirect pulse-vector control of wound rotor induction motor drive. The paper considers issues of thematic justification and expanding of the field of using sensorless motor drives. With a view to improve energy consumption readings during design and modernization of motor drives of massive mechanisms with moderate standards for accuracy of velocity control, requiring long-term velocity decrease during load reduction (according to technological process conditions), using the system of the pulse-vector control of wound rotor induction motor is suggested. The paper provides the solution for the problem of developing math models of this motor drive system both for the motor-mounted sensor, and for indirect angular position sensing. The models were developed in ANSYS Electromagnetics Suite using the finite element method for studying electromagnetic processes. Based on the models, the investigation of transition and steady states of a motor drive was carried out, process quality parameters were obtained, namely: max and root-mean-square currents, torques; velocity control errors caused by pulse operation mode. From that simulation, the result illustrates the effectiveness of the proposed approach.</span>
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Millo, Federico, Andrea Piano, Benedetta Peiretti Paradisi, Mario Rocco Marzano, Andrea Bianco, and Francesco C. Pesce. "Development and Assessment of an Integrated 1D-3D CFD Codes Coupling Methodology for Diesel Engine Combustion Simulation and Optimization." Energies 13, no. 7 (April 1, 2020): 1612. http://dx.doi.org/10.3390/en13071612.
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In this paper, an integrated and automated methodology for the coupling between 1D- and 3D-CFD simulation codes is presented, which has been developed to support the design and calibration of new diesel engines. The aim of the proposed methodology is to couple 1D engine models, which may be available in the early stage engine development phases, with 3D predictive combustion simulations, in order to obtain reliable estimates of engine performance and emissions for newly designed automotive diesel engines. The coupling procedure features simulations performed in 1D-CFD by means of GT-SUITE and in 3D-CFD by means of Converge, executed within a specifically designed calculation methodology. An assessment of the coupling procedure has been performed by comparing its results with experimental data acquired on an automotive diesel engine, considering different working points, including both part load and full load conditions. Different multiple injection schedules have been evaluated for part-load operation, including pre and post injections. The proposed methodology, featuring detailed 3D chemistry modeling, was proven to be capable assessing pollutant formation properly, specifically to estimate NOx concentrations. Soot formation trends were also well-matched for most of the explored working points. The proposed procedure can therefore be considered as a suitable methodology to support the design and calibration of new diesel engines, due to its ability to provide reliable engine performance and emissions estimations from the early stage of a new engine development.
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Martizzi, Davide. "Global simulations of galactic discs: violent feedback from clustered supernovae during bursts of star formation." Monthly Notices of the Royal Astronomical Society 492, no. 1 (December 5, 2019): 79–95. http://dx.doi.org/10.1093/mnras/stz3419.
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ABSTRACT A suite of idealized, global, gravitationally unstable, star-forming galactic disc simulations with 2 pc spatial resolution, performed with the adaptive mesh refinement code ramses, is used in this paper to predict the emergent effects of supernova feedback. The simulations include a simplified prescription for the formation of single stellar populations of mass $\sim 100 \, {\rm M}_{\odot }$, radiative cooling, photoelectric heating, an external gravitational potential for a dark matter halo and an old stellar disc, self-gravity, and a novel implementation of supernova feedback. The results of these simulations show that gravitationally unstable discs can generate violent supersonic winds with mass-loading factors η ≳ 10, followed by a galactic fountain phase. These violent winds are generated by highly clustered supernovae exploding in dense environments created by gravitational instability, and they are not produced in simulation without self-gravity. The violent winds significantly perturb the vertical structure of the disc, which is later re-established during the galactic fountain phase. Gas resettles into a quasi-steady, highly turbulent disc with volume-weighted velocity dispersion $\sigma \gt 50 \, {\rm km\, s}^{-1}$. The new configuration drives weaker galactic winds with a mass-loading factor η ≤ 0.1. The whole cycle takes place in ≤10 dynamical times. Such high time variability needs to be taken into account when interpreting observations of galactic winds from starburst and post-starburst galaxies.
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Astik, Noopur. "Dynamic Partial Reconfiguration with FIR Filter Application." International Journal of Reconfigurable and Embedded Systems (IJRES) 4, no. 3 (November 1, 2015): 201. http://dx.doi.org/10.11591/ijres.v4.i3.pp201-208.
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Dynamic partial reconfiguration has evolved as a very prominent state of art for efficient area utilization of <em>Field Programmable Gate Array</em> (FPGA) as well as significant reduction in its overall power consumption when properly used to lessen the idle logic on FPGA. It provides desired results even as the computational complexity increases in the field of Digital Signal Processing. This paper explains Dynamic Partial Reconfiguration (DPR) with an example of Finite Impulse response (FIR) filter of order 10. Initially RTL coding for Direct Form FIR structure is written in Verilog in fixed point format for low pass and high pass filter modules using ISE Design suite. Functioning of the both the modules is verified individually through hardware co-simulation on ZYBO (Zynq Board) from Digilent using Black Box from System Generator. Finally dynamic partial reconfigurable FIR filter with low pass and high pass as reconfigurable modules is implemented on ZYBO using PlanAhead tool. Final comparison of resource utilization with and without DPR is presented
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Meng, Xi, and Oleg Y. Gnedin. "Evolution of disc thickness in simulated high-redshift galaxies." Monthly Notices of the Royal Astronomical Society 502, no. 1 (January 15, 2021): 1433–40. http://dx.doi.org/10.1093/mnras/stab088.
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ABSTRACT We study the growth of stellar discs of Milky Way-sized galaxies using a suite of cosmological simulations. We calculate the half-mass axis lengths and axis ratios of stellar populations split by age in galaxies with stellar mass $M_{*}=10^7\!-\!10^{10}\, \mathrm{M}_{\odot }$ at redshifts z > 1.5. We find that in our simulations stars always form in relatively thin discs, and at ages below 100 Myr are contained within half-mass height z1/2 ∼ 0.1 kpc and short-to-long axial ratio z1/2/x1/2 ∼ 0.15. Disc thickness increases with the age of stellar population, reaching median z1/2 ∼ 0.8 kpc and z1/2/x1/2 ∼ 0.6 for stars older than 500 Myr. We trace the same group of stars over the simulation snapshots and show explicitly that their intrinsic shape grows more spheroidal over time. We identify a new mechanism that contributes to the observed disc thickness: rapid changes in the orientation of the galactic plane mix the configuration of young stars. The frequently mentioned ‘upside-down’ formation scenario of galactic discs, which posits that young stars form in already thick discs at high redshift, may be missing this additional mechanism of quick disc inflation. The actual formation of stars within a fairly thin plane is consistent with the correspondingly flat configuration of dense molecular gas that fuels star formation.
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Meng, Xi, and Oleg Y. Gnedin. "Origin of giant stellar clumps in high-redshift galaxies." Monthly Notices of the Royal Astronomical Society 494, no. 1 (March 20, 2020): 1263–75. http://dx.doi.org/10.1093/mnras/staa776.
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ABSTRACT We examine the nature of kpc-scale clumps seen in high-redshift galaxies using a suite of cosmological simulations of galaxy formation. We identify rest-frame UV clumps in mock HST images smoothed to 500 pc resolution, and compare them with the intrinsic 3D clumps of young stars identified in the simulations with 100 pc resolution. According to this comparison for the progenitors of Milky Way-sized galaxies probed by our simulations, we expect that the stellar masses of the observed clumps are overestimated by as much as an order of magnitude, and that the sizes of these clumps are also overestimated by factor of several, due to a combination of spatial resolution and projection. The masses of young stars contributing most of the UV emission can also be overestimated by factor of a few. We find that most clumps of young stars present in a simulation at one time dissolve on a timescale shorter than ∼150 Myr. Some clumps with dense cores can last longer but eventually disperse. Most of the clumps are not bound structures, with virial parameter αvir > 1. We find similar results for clumps identified in mock maps of H α emission measure. We examine the predictions for effective clump sizes from the linear theory of gravitational perturbations and conclude that they are inconsistent with being formed by global disc instabilities. Instead, the observed clumps represent random projections of multiple compact star-forming regions.
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Übler, Hannah, Shy Genel, Amiel Sternberg, Reinhard Genzel, Sedona H. Price, Natascha M. Förster Schreiber, Taro T. Shimizu, et al. "The kinematics and dark matter fractions of TNG50 galaxies at z = 2 from an observational perspective." Monthly Notices of the Royal Astronomical Society 500, no. 4 (November 10, 2020): 4597–619. http://dx.doi.org/10.1093/mnras/staa3464.
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ABSTRACT We contrast the gas kinematics and dark matter contents of z = 2 star-forming galaxies (SFGs) from state-of-the-art cosmological simulations within the ΛCDM framework to observations. To this end, we create realistic mock observations of massive SFGs ($M_*\gt 4\times 10^{10} \, \mathrm{M}_{\odot}$, SFR >50 M⊙ yr−1) from the TNG50 simulation of the IllustrisTNG suite, resembling near-infrared, adaptive-optics assisted integral-field observations from the ground. Using observational line fitting and modelling techniques, we analyse in detail the kinematics of seven TNG50 galaxies from five different projections per galaxy, and compare them to observations of twelve massive SFGs by Genzel et al. (2020). The simulated galaxies show clear signs of disc rotation but mostly exhibit more asymmetric rotation curves, partly due to large intrinsic radial and vertical velocity components. At identical inclination angle, their 1D velocity profiles can vary along different lines of sight by up to Δv = 200 km s−1. From dynamical modelling we infer rotation speeds and velocity dispersions that are broadly consistent with observational results. We find low central dark matter fractions compatible with observations ($f_{\rm DM}^v(\lt R_e)=v_{\rm DM}^2(R_e)/v_{\rm circ}^2(R_e)\sim 0.32\pm 0.10$), however for disc effective radii Re that are mostly too small: at fixed Re the TNG50 dark matter fractions are too high by a factor of ∼2. We speculate that the differences in gas kinematics and dark matter content compared to the observations may be due to physical processes that are not resolved in sufficient detail with the numerical resolution available in current cosmological simulations.
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Shin, Hyeyum Hailey, Domingo Muñoz-Esparza, Jeremy A. Sauer, and Matthias Steiner. "Large-Eddy Simulations of Stability-Varying Atmospheric Boundary Layer Flow over Isolated Buildings." Journal of the Atmospheric Sciences 78, no. 5 (May 2021): 1487–501. http://dx.doi.org/10.1175/jas-d-20-0160.1.
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AbstractThis study explores the response of flow around isolated cuboid buildings to variations in the incoming turbulence arising from changes in atmospheric boundary layer (ABL) stability using a building-resolving large-eddy simulation (LES) technique with explicit representation of building effects through an immersed body force method. An extensive suite of LES for a neutral ABL with different model resolution and advection scheme configurations reveals that at least 6, 12, and 24 grid points per building side are required in order to resolve building-induced vortex shedding, mean-flow features, and turbulence statistics, respectively, with an advection scheme of a minimum of third order. Using model resolutions that meet this requirement, 21 building-resolving simulations are performed under varying atmospheric stability conditions, from weakly stable to convective ABLs, and for different building sizes (H), resulting in LABL/H ≈ 0.1–10, where LABL is the integral length scale of the incoming ABL turbulence. The building-induced flow features observed in the canonical neutral ABL simulation, e.g., the upstream horseshoe vortex and the downstream arch vortex, gradually weaken with increasing surface-driven convective instability due to the enhancement of background turbulent mixing. As a result, two local turbulence kinetic energy peaks on the lateral side of the building in nonconvective cases are merged into a single peak in strong convective cases. By considering the ABL turbulence scale and building size altogether, it is shown that the building impact decreases with increasing LABL/H, as coherent turbulent structures in the ABL become more dominant over a building-induced flow response for LABL/H > 1.
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Calura, Francesco, Michele Bellazzini, and Annibale D’Ercole. "Hydrodynamic simulations of an isolated star-forming gas cloud in the Virgo cluster." Monthly Notices of the Royal Astronomical Society 499, no. 4 (October 15, 2020): 5873–90. http://dx.doi.org/10.1093/mnras/staa3133.
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ABSTRACT We present a suite of three-dimensional, high-resolution hydrodynamic simulations that follow the evolution of a massive (107 M⊙) pressure-confined, star-forming neutral gas cloud moving through a hot intracluster medium (ICM). The main goal of the analysis is to get theoretical insight into the lifetimes and evolution of stellar systems like the recently discovered star-forming cloud SECCO 1 in the Virgo cluster of galaxies, but it may be of general interest for the study of the star-forming gas clumps that are observed in the tails of ram pressure stripped galaxies. Building up on a previous, simple simulation, we explored the effect of different relative velocity of the cloud and larger temperature of the ICM, as well as the effect of the cloud self-gravity. Moreover, we performed a simulation including star formation and stellar feedback, allowing for a first time a direct comparison with the observed properties of the stars in the system. The survivability of the cold gas in the simulated clouds is granted on time-scales of the order of 1 Gyr, with final cold gas fractions generally >0.75. In all cases, the simulated systems end up, after 1 Gyr of evolution, as symmetric clouds in pressure equilibrium with the external hot gas. We also confirm that gravity played a negligible role at the largest scales on the evolution of the clouds. In our simulation with star formation, star formation begins immediately, it peaks at the earliest times, and decreases monotonically with time. Inhomogeneous supernova explosions are the cause of an asymmetric shape of the gas cloud, facilitating the development of instabilities and the decrease of the cold gas fraction.
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Reith, Fabian, Wolfgang Koeve, David P. Keller, Julia Getzlaff, and Andreas Oschlies. "Meeting climate targets by direct CO<sub>2</sub> injections: what price would the ocean have to pay?" Earth System Dynamics 10, no. 4 (November 7, 2019): 711–27. http://dx.doi.org/10.5194/esd-10-711-2019.
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Abstract. We investigate the climate mitigation potential and collateral effects of direct injections of captured CO2 into the deep ocean as a possible means to close the gap between an intermediate CO2 emissions scenario and a specific temperature target, such as the 1.5 ∘C target aimed for by the Paris Agreement. For that purpose, a suite of approaches for controlling the amount of direct CO2 injections at 3000 m water depth are implemented in an Earth system model of intermediate complexity. Following the representative concentration pathway RCP4.5, which is a medium mitigation CO2 emissions scenario, cumulative CO2 injections required to meet the 1.5 ∘C climate goal are found to be 390 Gt C by the year 2100 and 1562 Gt C at the end of simulations, by the year 3020. The latter includes a cumulative leakage of 602 Gt C that needs to be reinjected in order to sustain the targeted global mean temperature. CaCO3 sediment and weathering feedbacks reduce the required CO2 injections that comply with the 1.5 ∘C target by about 13 % in 2100 and by about 11 % at the end of the simulation. With respect to the injection-related impacts we find that average pH values in the surface ocean are increased by about 0.13 to 0.18 units, when compared to the control run. In the model, this results in significant increases in potential coral reef habitats, i.e., the volume of the global upper ocean (0 to 130 m depth) with omega aragonite > 3.4 and ocean temperatures between 21 and 28 ∘C, compared to the control run. The potential benefits in the upper ocean come at the expense of strongly acidified water masses at depth, with maximum pH reductions of about −2.37 units, relative to preindustrial levels, in the vicinity of the injection sites. Overall, this study demonstrates that massive amounts of CO2 would need to be injected into the deep ocean in order to reach and maintain the 1.5 ∘C climate target in a medium mitigation scenario on a millennium timescale, and that there is a trade-off between injection-related reductions in atmospheric CO2 levels accompanied by reduced upper-ocean acidification and adverse effects on deep-ocean chemistry, particularly near the injection sites.
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Koppelman, Helmer H., Roy O. Y. Bos, and Amina Helmi. "The messy merger of a large satellite and a Milky Way-like galaxy." Astronomy & Astrophysics 642 (October 2020): L18. http://dx.doi.org/10.1051/0004-6361/202038652.
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Aims. About 10 billion years ago the Milky Way merged with a massive satellite, Gaia-Enceladus. To gain insight into the properties of its debris we analyse in detail a suite of simulations that includes an experiment that produces a good match to the kinematics of nearby halo stars inferred from Gaia data. Methods. We compare the kinematic distributions of stellar particles in the simulations and study the distribution of debris in orbital angular momentum, eccentricity, and energy, and its relation to the mass loss history of the simulated satellite. Results. We confirm that Gaia-Enceladus probably fell in on a retrograde, 30° inclination orbit. We find that while 75% of the debris in our preferred simulation has high eccentricity (> 0.8), roughly 9% has eccentricity lower than 0.6. Star particles lost early have large retrograde motions, and a subset of these have low eccentricity. Such stars would be expected to have lower metallicities as they stem from the outskirts of the satellite, and hence naively they could be confused with debris associated with a separate system. These considerations seem to apply to some of the stars from the postulated Sequoia galaxy. Conclusions. When a massive disc galaxy undergoes a merger event, it leaves behind debris with a complex phase-space structure, a wide range of orbital properties, and a range of chemical abundances. Observationally, this results in substructures with very different properties, which can be misinterpreted as implying independent progeny. Detailed chemical abundances of large samples of stars and tailored hydrodynamical simulations are critical to resolving such conundrums.
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Raza, Waseem, Gwang Soo Ko, and Youn Cheol Park. "Performance Evaluation of Battery Thermal Management System in Electric Vehicle using Induction Heater (Part 1: Parallel System)." International Journal of Air-Conditioning and Refrigeration 28, no. 01 (January 30, 2020): 2050003. http://dx.doi.org/10.1142/s2010132520500030.
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The fast evolving Electric vehicles (EVs) have become popular due to their zero-emission, fuel economy and better technology. However, the performance and life of batteries are very sensitive to temperature, it is important to maintain the proper temperature range. The battery thermal management system (BTMS) plays an important role in the performance of EVs. In this context, this study is conducted to evaluate the thermal performance of a battery with a parallel system using an induction heater. The GT-Suite software is used for simulation and evaluation. Mixture of water and ethylene glycol 50:50 is used as a working fluid and controlled by pump and valves. The heating rate of battery was analyzed by changing the capacity of induction heater 2, 4 and 6[Formula: see text]kW and the flow rate of fluid was 2, 3, 5, 7, 10 and 27 LPM. The simulation work predicts that the battery heating rate increases with the increase in fluid flow. The study concluded that the battery heating rate is maximum with a flow rate of 27 LPM which is the highest amount of LPM, indicating that the rise in flow rate causes the increase in heating rate of the system which is also affected by induction heater capacity.
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Hussain, Md Zakir, and Kazi Nikhat Parvin. "Low power and high performance FFT with different radices." International Journal of Reconfigurable and Embedded Systems (IJRES) 8, no. 2 (July 1, 2019): 99. http://dx.doi.org/10.11591/ijres.v8.i2.pp99-106.
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<p>FFT is one of the most active blocks in digital signal processing and in various field of communication systems. FFT has received significant attention over the past years to increase its capability and versatility. This paper describes an extensive study on trade-off of different radices with different computational elements of butterfly such as adders and multipliers. Finding an efficient radix along with computational elements is the key point to find best suite i.e. high precision, low power and low area applications like radar, filtering, image compression etc. The work also considers the precision and the data format to represent constant value such as Q-point. The proposed FFT architectures not only uphold better solutions for low power and high-performance application systems, but also open up a new research lines. This paper demonstrates that radix-2^3 consumes 43% less LUTs and 17% less power consumption, 40% increase of frequency in radix-2^2 in comparison with radix- 2 algorithm for the combination of CSA with modified booth multiplier and the increment of frequency about 19%, 26% less LUTs consumption and 26% less power in Radix-2^2 when compared to radix-4 with various combination of adder and multiplier. In this work we have used Xilinx 14.7 XST for synthesis and the target device used is Spartan6 XC6SLX100. Simulation is carried out in Xilinx ISIM and also performed timing analysis and generated post-place and route.</p>
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Mukherjee, Sampath, Léon V. E. Koopmans, R. Benton Metcalf, Cresenzo Tortora, Matthieu Schaller, Joop Schaye, Georgios Vernardos, and Fabio Bellagamba. "SEAGLE – II. Constraints on feedback models in galaxy formation from massive early-type strong-lens galaxies." Monthly Notices of the Royal Astronomical Society 504, no. 3 (March 10, 2021): 3455–77. http://dx.doi.org/10.1093/mnras/stab693.
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ABSTRACT We use nine different galaxy formation scenarios in ten cosmological simulation boxes from the EAGLE (Evolution and Assembly of GaLaxies and their Environments) suite of Lambda cold dark matter hydrodynamical simulations to assess the impact of feedback mechanisms in galaxy formation and compare these to observed strong gravitational lenses. To compare observations with simulations, we create strong lenses with M* > 1011 M⊙ with the appropriate resolution and noise level, and model them with an elliptical power-law mass model to constrain their total mass density slope. We also obtain the mass–size relation of the simulated lens-galaxy sample. We find significant variation in the total mass density slope at the Einstein radius and in the projected stellar mass–size relation, mainly due to different implementations of stellar and active galactic nucleus (AGN) feedback. We find that for lens-selected galaxies, models with either too weak or too strong stellar and/or AGN feedback fail to explain the distribution of observed mass density slopes, with the counter-intuitive trend that increasing the feedback steepens the mass density slope around the Einstein radius (≈3–10 kpc). Models in which stellar feedback becomes inefficient at high gas densities, or weaker AGN feedback with a higher duty cycle, produce strong lenses with total mass density slopes close to isothermal [i.e. −dlog (ρ)/dlog (r) ≈ 2.0] and slope distributions statistically agreeing with observed strong-lens galaxies in Sloan Lens ACS Survey and BOSS (Baryon Oscillation Spectroscopic Survey) Emission-Line Lens Survey. Agreement is only slightly worse with the more heterogeneous Strong Lensing Legacy Survey lens-galaxy sample. Observations of strong-lens-selected galaxies thus appear to favour models with relatively weak feedback in massive galaxies.
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Terrazas, Bryan A., Eric F. Bell, Annalisa Pillepich, Dylan Nelson, Rachel S. Somerville, Shy Genel, Rainer Weinberger, et al. "The relationship between black hole mass and galaxy properties: examining the black hole feedback model in IllustrisTNG." Monthly Notices of the Royal Astronomical Society 493, no. 2 (February 19, 2020): 1888–906. http://dx.doi.org/10.1093/mnras/staa374.
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ABSTRACT Supermassive black hole feedback is thought to be responsible for the lack of star formation, or quiescence, in a significant fraction of galaxies. We explore how observable correlations between the specific star formation rate (sSFR), stellar mass (Mstar), and black hole mass (MBH) are sensitive to the physics of black hole feedback in a galaxy formation model. We use the IllustrisTNG simulation suite, specifically the TNG100 simulation and 10 model variations that alter the parameters of the black hole model. Focusing on central galaxies at z = 0 with Mstar > 1010 M⊙, we find that the sSFR of galaxies in IllustrisTNG decreases once the energy from black hole kinetic winds at low accretion rates becomes larger than the gravitational binding energy of gas within the galaxy stellar radius. This occurs at a particular MBH threshold above which galaxies are found to sharply transition from being mostly star forming to mostly quiescent. As a result of this behaviour, the fraction of quiescent galaxies as a function of Mstar is sensitive to both the normalization of the MBH–Mstar relation and the MBH threshold for quiescence in IllustrisTNG. Finally, we compare these model results to observations of 91 central galaxies with dynamical MBH measurements with the caveat that this sample is not representative of the whole galaxy population. While IllustrisTNG reproduces the observed trend that quiescent galaxies host more massive black holes, the observations exhibit a broader scatter in MBH at a given Mstar and show a smoother decline in sSFR with MBH.
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Pulsoni, C., O. Gerhard, M. Arnaboldi, A. Pillepich, V. Rodriguez-Gomez, D. Nelson, L. Hernquist, and V. Springel. "The stellar halos of ETGs in the IllustrisTNG simulations." Astronomy & Astrophysics 647 (March 2021): A95. http://dx.doi.org/10.1051/0004-6361/202039166.
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Stellar halos in early-type galaxies (ETGs) are shaped by their accretion and merger histories. We use a sample of 1114 ETGs in the TNG100 simulation of the IllustrisTNG suite with stellar masses 1010.3 ≤ M*/M⊙ ≤ 1012, selected at z = 0 within the range of the g − r colour and λ-ellipticity diagram populated by observed ETGs. We study how the rotational support and intrinsic shapes of the stellar halos depend on the fraction of stars accreted, both overall and separately, by major, minor, and mini mergers. Accretion histories in TNG100 ETGs as well as the final radial distributions of ex-situ stars fexsitu(R) relative to in-situ (“accretion classes”) strongly correlate with stellar mass. Low-mass galaxies have characteristic peaked rotation profiles and near-oblate shapes with rounder halos that are completely driven by the in-situ stars. At high fexsitu, major mergers decrease the in-situ peak in rotation velocity, flatten the V*/σ*(R) profiles, and increase the triaxiality of the stellar halos. Kinematic transition radii do not trace the transition between in-situ- and ex-situ-dominated regions, but for systems with M* > 1010.6 M⊙ the local rotational support of the stellar halos decreases with the local ex-situ fraction fexsitu(R) at fixed M*, and their triaxiality increases with fexsitu(R). These correlations between rotational support, intrinsic shapes, and local fexsitu are followed by fast and slow rotators alike with a continuous and overlapping sequence of properties, but slow rotators are concentrated at the high-fexsitu end dominated by dry major mergers. We find that in ∼20% of high-mass ETGs, the central regions are dominated by stars from a high-redshift compact progenitor. Merger events dynamically couple stars and dark matter: in high-mass galaxies and at large radii where fexsitu ≳ 0.5, both components tend to have similar intrinsic shapes and rotational support, and nearly aligned principal axes and spin directions. Based on these results we suggest that extended photometry and kinematics of massive ETGs (M* > 1010.6 M⊙) can be used to estimate the local fraction of ex-situ stars, and to approximate the intrinsic shapes and rotational support of the co-spatial dark matter component.
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Han, Yong Qiang, Jiao Zeng, and Chuan Qiao. "The Model of a Free Piston System Based Organic Rankine Cycle and the Analysis of Sensitive Factors." Advanced Materials Research 732-733 (August 2013): 368–75. http://dx.doi.org/10.4028/www.scientific.net/amr.732-733.368.
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For recycling complementary energy efficiently, WMs latent heat of vaporization is made full use of in a free piston based organic rankine cycle exhaust gas energy recovery (ORC-FP) system. In this paper, the model of ORC-FP system has been established by the software GT-suite 7.0. Three sensitive factors (WMs gas ratio, piston damping coefficient and power WMs pressure) will be discussed by simulation results. The conclusions are shown as follows: Firstly, when WM state is 450K, 1.1MPa (Power WM) and 320K, 1.1MPa (Cooling WM) at inlet, the systems single cycle efficiency is highest about 69.21%, and the lowest is about 42.32%. Certain fluctuation of single cycle (SC) efficiency exists between two adjacent cycle, and the highest difference can reach 26.89%. Secondly, the systems total cycle (TC) efficiency decreases along with the increasing of damping coefficient (piston load). At the minimum piston damping coefficient (about 7500 N-s/m), the systems highest total cycle efficiency is 46.53%, and at the maximum (about 8750 N - s/m), the lowest total cycle efficiency is 35.66%. Thirdly, when damping coefficient is 7500 N-s/m, the higher pressure of WM is, the higher the systems total cycle efficiency is. In the pressure of 1.1MPa, the system reaches the highest efficiency which is about 46.53%, and in the pressure of 0.9 MPa reaches the lowest which is about 26.74%.
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Kohel, Petr, and Rastislav Toman. "DEVELOPMENT OF A CONTROL ALGORITHM FOR A PARALLEL HYBRID POWERTRAIN." MECCA Journal of Middle European Construction and Design of Cars 17, no. 1 (July 20, 2020): 14. http://dx.doi.org/10.14311/mecdc.2020.01.03.
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The current legislation calls for fast electrification of vehicle powertrains, since it is necessary to fulfil the CO2 requirements for the vehicle fleets. The hybrid electric vehicles (HEV) with parallel powertrain topologies – together with pure battery electric vehicles (BEV) – are the most common ways of electrification. However, the HEV powertrain – opposed to the BEV or conventional powertrain – poses an interesting challenge associated with the control system design to achieve the ideal power split between an internal combustion engine (ICE) and electrical machines (EM) during the whole vehicle operation.The presented paper sums up the specific functions and requirements on a control system, together with the description of general control strategy options for a HEV powertrain. The proposed control strategy then combines heuristic rules with a suboptimal numerical control method, calculating the optimal power split ratio based on the efficiencies of ICE and EMs. This control strategy is built into a modular algorithm in Matlab/Simulink for two different parallel HEV powertrain topologies: P2 and P0P4. It is subsequently coupled with a vehicle models created in GT-Suite environment and tested on a WLTC homologation driving cycles. The following simulation tests show the fuel consumption reduction potential for chosen HEV topologies working in hybrid modes, in comparison to a base operation with conventional mode only. Yet, the heuristic rules can be further optimized to obtain even better overall results.Současná legislativa tlačí výrobce vozidel k okamžité elektrifikaci pohonu, protože je to v tuto chvíli jediná možnost, jak dostát požadavkům na flotilové emise CO2. Nejběžnější formou elektrifikace pohonu jsou v dnešní době vozidla s paralelním hybridním pohonem anebo bateriové elektromobily. Nicméně hybridní pohon, na rozdíl právě od konvenčního nebo čistě elektrického pohonu, představuje zajímavé výzvy spojené s návrhem řídicího algoritmu, který musí v každém okamžiku zajišťovat optimální rozdělení výkonu mezi spalovací motor a elektromotor.Tento článek v úvodu krátce shrnuje specifické funkce a požadavky na takový řídicí algoritmus, společně s obecným přehledem možných řídicích strategií hybridních vozidel. Následně je navržena řídicí strategie kombinující heuristická pravidla se suboptimální numerickou metodou, která vypočítává parametr optimálního dělení výkonu na základě účinností spalovacího motoru a elektromotoru. Na základě navrhnuté strategie je v programu Matlab/Simulink vytvořen modulární řídicí algoritmus pro dvě paralelní hybridní topologie: P2 a P0P4, který je následně propojen s modely vozidel vytvořenými v simulačním prostředí GT-Suite a testován v homologačním cyklu WLTC. Nakonec je prezentováno několik testů řídicího algoritmu, které demonstrují úsporu paliva vybraných topologií hybridního vozidla pracujících v hybridních režimech, ve srovnání s provozem pouze v konvenčním režimu pohonu. Avšak heuristická pravidla mohou být dále optimalizována, s cílem dosáhnout ještě příznivějších celkových výsledků.
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Bastian, Nate, Joel Pfeffer, J. M. Diederik Kruijssen, Robert A. Crain, Sebastian Trujillo-Gomez, and Marta Reina-Campos. "The globular cluster system mass–halo mass relation in the E-MOSAICS simulations." Monthly Notices of the Royal Astronomical Society 498, no. 1 (August 19, 2020): 1050–61. http://dx.doi.org/10.1093/mnras/staa2453.
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ABSTRACT Linking globular clusters (GCs) to the assembly of their host galaxies is an overarching goal in GC studies. The inference of tight scaling relations between GC system properties and the mass of both the stellar and dark halo components of their host galaxies are indicative of an intimate physical connection, yet have also raised fundamental questions about how and when GCs form. Specifically, the inferred correlation between the mass of a GC system (MGC) and the dark matter halo mass (Mhalo) of a galaxy has been posited as a consequence of a causal relation between the formation of dark matter mini-haloes and GC formation during the early epochs of galaxy assembly. We present the first results from a new simulation of a cosmological volume (L = 34.4 cMpc on a side) from the E-MOSAICS suite, which includes treatments of the formation and evolution of GCs within the framework of a detailed galaxy formation model. The simulated MGC–Mhalo relation is linear for halo masses >5 × 1011 M⊙, and is driven by the hierarchical assembly of galaxies. Below this halo mass, the simulated relation features a downturn, which we show is consistent with observations, and is driven by the underlying stellar mass–halo mass relation of galaxies. Our fiducial model reproduces the observed MGC–M⋆ relation across the full mass range, which we argue is more physically relevant than the MGC–Mhalo relation. We also explore the physical processes driving the observed constant value of $\hbox{$M_{\rm GC}$}/ \hbox{$M_{\rm halo}$}\sim 5\times 10^{-5}$ and find that it is the result of a combination of cluster formation physics and cluster disruption.
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Dudchenko, Alexander V., Timothy V. Bartholomew, and Meagan S. Mauter. "High-impact innovations for high-salinity membrane desalination." Proceedings of the National Academy of Sciences 118, no. 37 (September 7, 2021): e2022196118. http://dx.doi.org/10.1073/pnas.2022196118.
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Reducing the cost of high-salinity (>75 g/L total dissolved solids) brine concentration technology would unlock the potential for vast inland water supplies and promote the safe management of concentrated aqueous waste streams. Impactful innovation will target component performance improvements and cost reductions that yield the highest impact on system costs, but the desalination community lacks methods for quantitatively evaluating the value of innovation or the robustness of technology platforms relative to competing technologies. This work proposes a suite of methods built on process-based cost optimization models that explicitly address the complexities of membrane-separation processes, namely that these processes comprise dozens of nonlinearly interacting components and that innovation can occur in more than one component at a time. We begin by demonstrating the merit of performing simple parametric sensitivity analysis on component performance and cost to guide the selection of materials and manufacturing methods that reduce system costs. A more rigorous implementation of this approach relates improvements in component performance to increases in component costs, helping to further discern high-impact innovation trajectories. The most advanced implementation includes a stochastic simulation of the value of innovation that accounts for both the expected impact of a component innovation on reducing system costs and the potential for improvements in other components. Finally, we apply these methods to identify innovations with the highest probability of substantially reducing the levelized cost of water from emerging membrane processes for high-salinity brine treatment.
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Zhou, Sha, Junyi Liang, Xingjie Lu, Qianyu Li, Lifen Jiang, Yao Zhang, Christopher R. Schwalm, et al. "Sources of Uncertainty in Modeled Land Carbon Storage within and across Three MIPs: Diagnosis with Three New Techniques." Journal of Climate 31, no. 7 (April 2018): 2833–51. http://dx.doi.org/10.1175/jcli-d-17-0357.1.
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Terrestrial carbon cycle models have incorporated increasingly more processes as a means to achieve more-realistic representations of ecosystem carbon cycling. Despite this, there are large across-model variations in the simulation and projection of carbon cycling. Several model intercomparison projects (MIPs), for example, the fifth phase of the Coupled Model Intercomparison Project (CMIP5) (historical simulations), Trends in Net Land–Atmosphere Carbon Exchange (TRENDY), and Multiscale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP), have sought to understand intermodel differences. In this study, the authors developed a suite of new techniques to conduct post-MIP analysis to gain insights into uncertainty sources across 25 models in the three MIPs. First, terrestrial carbon storage dynamics were characterized by a three-dimensional (3D) model output space with coordinates of carbon residence time, net primary productivity (NPP), and carbon storage potential. The latter represents the potential of an ecosystem to lose or gain carbon. This space can be used to measure how and why model output differs. Models with a nitrogen cycle generally exhibit lower annual NPP in comparison with other models, and mostly negative carbon storage potential. Second, a transient traceability framework was used to decompose any given carbon cycle model into traceable components and identify the sources of model differences. The carbon residence time (or NPP) was traced to baseline carbon residence time (or baseline NPP related to the maximum carbon input), environmental scalars, and climate forcing. Third, by applying a variance decomposition method, the authors show that the intermodel differences in carbon storage can be mainly attributed to the baseline carbon residence time and baseline NPP (>90% in the three MIPs). The three techniques developed in this study offer a novel approach to gain more insight from existing MIPs and can point out directions for future MIPs. Since this study is conducted at the global scale for an overview on intermodel differences, future studies should focus more on regional analysis to identify the sources of uncertainties and improve models at the specified mechanism level.
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Raza, Waseem, Gwang Soo Ko, and Youn Cheol Park. "Induction Heater Based Battery Thermal Management System for Electric Vehicles." Energies 13, no. 21 (October 31, 2020): 5711. http://dx.doi.org/10.3390/en13215711.
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The life and efficiency of electric vehicle batteries are susceptible to temperature. The impact of cold climate dramatically decreases battery life, while at the same time increasing internal impedance. Thus, a battery thermal management system (BTMS) is vital to heat and maintain temperature range if the electric vehicle’s batteries are operating in a cold climate. This paper presents an induction heater-based battery thermal management system that aims to ensure thermal safety and prolong the life cycle of Lithium-ion batteries (Li-Bs). This study used a standard simulation tool known as GT-Suite to simulate the behavior of the proposed BTMS. For the heat transfer, an indirect liquid heating method with variations in flow rate was considered between Lithium-ion batteries. The battery and cabin heating rate was analyzed using the induction heater powers of 2, 4, and 6 kW at ambient temperatures of −20, −10, and 0 °C. A water and ethylene glycol mixture with a ratio of 50:50 was considered as an operating fluid. The findings reveal that the thermal performance of the proposed system is generally increased by increasing the flow rate and affected by the induction heater capacity. It is evident that at −20 °C with 27 LPM and 6 kW heater capacity, the maximum heat transfer rate is 0.0661 °C/s, whereas the lowest is 0.0295 °C/s with 2 kW heater capacity. Furthermore, the proposed BTMS could be a practical approach and help to design the thermal system for electric vehicles in the future.
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Renneby, Malin, Bruno M. B. Henriques, Stefan Hilbert, Dylan Nelson, Mark Vogelsberger, Raúl E. Angulo, Volker Springel, and Lars Hernquist. "Joint galaxy–galaxy lensing and clustering constraints on galaxy formation." Monthly Notices of the Royal Astronomical Society 498, no. 4 (September 4, 2020): 5804–33. http://dx.doi.org/10.1093/mnras/staa2675.
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ABSTRACT We compare predictions for galaxy–galaxy lensing profiles and clustering from the Henriques et al. public version of the Munich semi-analytical model (SAM) of galaxy formation and the IllustrisTNG suite, primarily TNG300, with observations from KiDS + GAMA and SDSS-DR7 using four different selection functions for the lenses (stellar mass, stellar mass and group membership, stellar mass and isolation criteria, and stellar mass and colour). We find that this version of the SAM does not agree well with the current data for stellar mass-only lenses with $M_\ast \gt 10^{11}\, \mathrm{ M}_\odot$. By decreasing the merger time for satellite galaxies as well as reducing the radio-mode active galactic nucleus accretion efficiency in the SAM, we obtain better agreement, both for the lensing and the clustering, at the high-mass end. We show that the new model is consistent with the signals for central galaxies presented in Velliscig et al. Turning to the hydrodynamical simulation, TNG300 produces good lensing predictions, both for stellar mass-only (χ2 = 1.81 compared to χ2 = 7.79 for the SAM) and locally brightest galaxy samples (χ2 = 3.80 compared to χ2 = 5.01). With added dust corrections to the colours it matches the SDSS clustering signal well for red low-mass galaxies. We find that both the SAMs and TNG300 predict $\sim 50\, {{\ \rm per\ cent}}$ excessive lensing signals for intermediate-mass red galaxies with 10.2 < log10M*[M⊙] < 11.2 at $r \approx 0.6\, h^{-1}\, \text{Mpc}$, which require further theoretical development.
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Li, Yang, and Xiaohong Jiao. "Energy management strategy for hybrid electric vehicles based on adaptive equivalent consumption minimization strategy and mode switching with variable thresholds." Science Progress 103, no. 1 (September 27, 2019): 003685041987499. http://dx.doi.org/10.1177/0036850419874992.
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To improve the real-time capability, adaptivity, and efficiency of the energy management strategy in the actual driving cycle, a real-time energy management strategy is investigated for commute hybrid electric vehicles, which integrates mode switching with variable threshold and adaptive equivalent consumption minimization strategy. The proposed strategy includes offline and online parts. In the offline part based on the historical traffic data on the route of the commute vehicle, particle swarm optimization is applied to optimize all the thresholds of mode switching, equivalence factor of the equivalent consumption minimization strategy, and the engine torque and speed at the engine-alone propelling mode so as to establish their mappings on the battery state of charge and power demand. In the online part, the established mappings are involved in the energy management supervisor to generate timely appropriate mode switching signals, and an adaptive equivalence factor for instantaneous optimization equivalent consumption minimization strategy and the optimal engine torque and speed at engine-alone propelling mode. To fully demonstrate the effectiveness of the proposed strategy, the simulation results and comparison with some other strategies and the benchmark dynamic programming strategy are presented by implementing the strategies on the GT-SUITE test platform. The comparison result indicates that the control effect of the proposed energy management strategy is much nearer to that of the benchmark dynamic programming than those of other strategies (the rule-based control, the conventional equivalent consumption minimization strategy, the adaptive equivalent consumption minimization strategy, the rule-based-equivalent consumption minimization strategy, and the stochastic dynamic programming strategy) with the respective improvement in fuel efficiency by 25.9%, 13.25%, 4.6%, 1.32%, and 1.13%.
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Hiranuma, Naruki, Ottmar Möhler, Gourihar Kulkarni, Martin Schnaiter, Steffen Vogt, Paul Vochezer, Emma Järvinen, et al. "Development and characterization of an ice-selecting pumped counterflow virtual impactor (IS-PCVI) to study ice crystal residuals." Atmospheric Measurement Techniques 9, no. 8 (August 18, 2016): 3817–36. http://dx.doi.org/10.5194/amt-9-3817-2016.
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Abstract. Separation of particles that play a role in cloud activation and ice nucleation from interstitial aerosols has become necessary to further understand aerosol-cloud interactions. The pumped counterflow virtual impactor (PCVI), which uses a vacuum pump to accelerate the particles and increase their momentum, provides an accessible option for dynamic and inertial separation of cloud elements. However, the use of a traditional PCVI to extract large cloud hydrometeors is difficult mainly due to its small cut-size diameters (< 5 µm). Here, for the first time we describe a development of an ice-selecting PCVI (IS-PCVI) to separate ice in controlled mixed-phase cloud system based on the particle inertia with the cut-off diameter ≥ 10 µm. We also present its laboratory application demonstrating the use of the impactor under a wide range of temperature and humidity conditions. The computational fluid dynamics simulations were initially carried out to guide the design of the IS-PCVI. After fabrication, a series of validation laboratory experiments were performed coupled with the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) expansion cloud simulation chamber. In the AIDA chamber, test aerosol particles were exposed to the ice supersaturation conditions (i.e., RHice > 100 %), where a mixture of droplets and ice crystals was formed during the expansion experiment. In parallel, the flow conditions of the IS-PCVI were actively controlled, such that it separated ice crystals from a mixture of ice crystals and cloud droplets, which were of diameter ≥ 10 µm. These large ice crystals were passed through the heated evaporation section to remove the water content. Afterwards, the residuals were characterized with a suite of online and offline instruments downstream of the IS-PCVI. These results were used to assess the optimized operating parameters of the device in terms of (1) the critical cut-size diameter, (2) the transmission efficiency and (3) the counterflow-to-input flow ratio. Particle losses were characterized by comparing the residual number concentration to the rejected interstitial particle number concentration. Overall results suggest that the IS-PCVI enables inertial separation of particles with a volume-equivalent particle size in the range of ~ 10–30 µm in diameter with small inadvertent intrusion (~ 5 %) of unwanted particles.
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Vogelsberger, Mark, Dylan Nelson, Annalisa Pillepich, Xuejian Shen, Federico Marinacci, Volker Springel, Rüdiger Pakmor, et al. "High-redshift JWST predictions from IllustrisTNG: dust modelling and galaxy luminosity functions." Monthly Notices of the Royal Astronomical Society 492, no. 4 (January 16, 2020): 5167–201. http://dx.doi.org/10.1093/mnras/staa137.
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ABSTRACT The James Webb Space Telescope (JWST) promises to revolutionize our understanding of the early Universe, and contrasting its upcoming observations with predictions of the Λ cold dark matter model requires detailed theoretical forecasts. Here, we exploit the large dynamic range of the IllustrisTNG simulation suite, TNG50, TNG100, and TNG300, to derive multiband galaxy luminosity functions from z = 2 to z = 10. We put particular emphasis on the exploration of different dust attenuation models to determine galaxy luminosity functions for the rest-frame ultraviolet (UV), and apparent wide NIRCam bands. Our most detailed dust model is based on continuum Monte Carlo radiative transfer calculations employing observationally calibrated dust properties. This calibration results in constraints on the redshift evolution of the dust attenuation normalization and dust-to-metal ratios yielding a stronger redshift evolution of the attenuation normalization compared to most previous theoretical studies. Overall we find good agreement between the rest-frame UV luminosity functions and observational data for all redshifts, also beyond the regimes used for the dust model calibrations. Furthermore, we also recover the observed high-redshift (z = 4–6) UV luminosity versus stellar mass relation, the H α versus star formation rate relation, and the H α luminosity function at z = 2. The bright end (MUV > −19.5) cumulative galaxy number densities are consistent with observational data. For the F200W NIRCam band, we predict that JWST will detect ∼80 (∼200) galaxies with a signal-to-noise ratio of 10 (5) within the NIRCam field of view, $2.2\times 2.2 \, {\rm arcmin}^{2}$, for a total exposure time of $10^5\, {\rm s}$ in the redshift range z = 8 ± 0.5. These numbers drop to ∼10 (∼40) for an exposure time of $10^4\, {\rm s}$.
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Móring, A., M. Vieno, R. M. Doherty, J. Laubach, A. Taghizadeh-Toosi, and M. A. Sutton. "A process-based model for ammonia emission from urine patches, GAG (Generation of Ammonia from Grazing): description, validation and sensitivity analysis." Biogeosciences Discussions 12, no. 13 (July 8, 2015): 10059–113. http://dx.doi.org/10.5194/bgd-12-10059-2015.
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Abstract. In this paper a new process-based, weather-driven model for ammonia (NH3) emission from a urine patch has been developed and its sensitivity to various factors assessed. This model, the GAG model (Generation of Ammonia from Grazing) was developed as a part of a suite of weather-driven NH3 exchange models, as a necessary basis for assessing the effects of climate change on NH3 related atmospheric processes. GAG is capable of simulating the TAN (Total Ammoniacal Nitrogen) content, pH and the water content of the soil under a urine patch. To calculate the TAN budget, GAG takes into account urea hydrolysis as a TAN input and NH3 volatilization as a loss. In the water budget, in addition to the water content of urine, precipitation and evaporation are also considered. In the pH module we assumed that the main regulating processes are the dissociation and dissolution equilibria related to the two products of urea hydrolysis: ammonium and bicarbonate. Finally, in the NH3 exchange flux calculation we adapted a canopy compensation point model that accounts for exchange with soil pores and stomata as well as deposition to the leaf surface. We validated our model against measurements, and carried out a sensitivity analysis. The validation showed that the simulated parameters (NH3 exchange flux, soil pH, TAN budget and water budget) are well captured by the model (r > 0.5 for every parameter at p < 0.01 significance level). We found that process-based modelling of pH is necessary to reproduce the temporal development of NH3 emission. In addition, our results suggested that more sophisticated simulation of CO2 emission in the model could potentially improve the modelling of pH. The sensitivity analysis highlighted the vital role of temperature in NH3 exchange; however, presumably due to the TAN limitation, the GAG model currently provides only a modest overall temperature dependence in total NH3 emission compared with the values in the literature. Since all the input parameters can be obtained for study at larger scales, GAG is potentially suitable for larger scale application, such as in regional atmospheric and ecosystem models.
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Kerviel, Arthur, Apostolos Pesyridis, Ahmed Mohammed, and David Chalet. "An Evaluation of Turbocharging and Supercharging Options for High-Efficiency Fuel Cell Electric Vehicles." Applied Sciences 8, no. 12 (December 3, 2018): 2474. http://dx.doi.org/10.3390/app8122474.
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Mass-produced, off-the-shelf automotive air compressors cannot be directly used for boosting a fuel cell vehicle (FCV) application in the same way that they are used in internal combustion engines, since the requirements are different. These include a high pressure ratio, a low mass flow rate, a high efficiency requirement, and a compact size. From the established fuel cell types, the most promising for application in passenger cars or light commercial vehicle applications is the proton exchange membrane fuel cell (PEMFC), operating at around 80 °C. In this case, an electric-assisted turbocharger (E-turbocharger) and electric supercharger (single or two-stage) are more suitable than screw and scroll compressors. In order to determine which type of these boosting options is the most suitable for FCV application and assess their individual merits, a co-simulation of FCV powertrains between GT-SUITE and MATLAB/SIMULINK is realised to compare vehicle performance on the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) driving cycle. The results showed that the vehicle equipped with an E-turbocharger had higher performance than the vehicle equipped with a two-stage compressor in the aspects of electric system efficiency (+1.6%) and driving range (+3.7%); however, for the same maximal output power, the vehicle’s stack was 12.5% heavier and larger. Then, due to the existence of the turbine, the E-turbocharger led to higher performance than the single-stage compressor for the same stack size. The solid oxide fuel cell is also promising for transportation application, especially for a use as range extender. The results show that a 24-kWh electric vehicle can increase its driving range by 252% due to a 5 kW solid oxide fuel cell (SOFC) stack and a gas turbine recovery system. The WLTP driving range depends on the charge cycle, but with a pure hydrogen tank of 6.2 kg, the vehicle can reach more than 600 km.
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Han, Lu, Xiaohong Jiao, and Zhao Zhang. "Recurrent Neural Network-Based Adaptive Energy Management Control Strategy of Plug-In Hybrid Electric Vehicles Considering Battery Aging." Energies 13, no. 1 (January 1, 2020): 202. http://dx.doi.org/10.3390/en13010202.
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A hybrid electric vehicle (HEV) is a product that can greatly alleviate problems related to the energy crisis and environmental pollution. However, replacing such a battery will increase the cost of usage before the end of the life of a HEV. Thus, research on the multi-objective energy management control problem, which aims to not only minimize the gasoline consumption and consumed electricity but also prolong battery life, is necessary and challenging for HEV. This paper presents an adaptive equivalent consumption minimization strategy based on a recurrent neural network (RNN-A-ECMS) to solve the multi-objective optimal control problem for a plug-in HEV (PHEV). The two objectives of energy consumption and battery loss are balanced in the cost function by a weighting factor that changes in real time with the operating mode and current state of the vehicle. The near-global optimality of the energy management control is guaranteed by the equivalent factor (EF) in the designed A-ECMS. As the determined EF is dependent on the optimal co-state of the Pontryagin’s minimum principle (PMP), which results in the online ECMS being regarded as a realization of PMP-based global optimization during the whole driving cycle. The time-varying weight factor and the co-state of the PMP are map tables on the state of charge (SOC) of the battery and power demand, which are established offline by the particle swarm optimization (PSO) algorithm and real historical traffic data. In addition to the mappings of the weight factor and the major component of the EF linked to the optimal co-state of the PMP, the real-time performance of the energy management control is also guaranteed by the tuning component of the EF of A-ECMS resulting from the Proportional plus Integral (PI) control on the deviation between the battery SOC and the optimal trajectory of the SOC obtained by the Recurrent Neural Network (RNN). The RNN is trained offline by the SOC trajectory optimized by dynamic programming (DP) utilizing the historical traffic data. Finally, the effectiveness and the adaptability of the proposed RNN-A-ECMS are demonstrated on the test platform of plug-in hybrid electric vehicles based on GT-SUITE (a professional integrated simulation platform for engine/vehicle systems developed by Gamma Technologies of US company) compared with the existing strategy.
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Zhu, Jian, Shanshan Wang, Hongli Wang, Shengao Jing, Shengrong Lou, Alfonso Saiz-Lopez, and Bin Zhou. "Observationally constrained modeling of atmospheric oxidation capacity and photochemical reactivity in Shanghai, China." Atmospheric Chemistry and Physics 20, no. 3 (February 3, 2020): 1217–32. http://dx.doi.org/10.5194/acp-20-1217-2020.
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Abstract. An observation-based model coupled to the Master Chemical Mechanism (V3.3.1) and constrained by a full suite of observations was developed to study atmospheric oxidation capacity (AOC), OH reactivity, OH chain length and HOx (=OH+HO2) budget for three different ozone (O3) concentration levels in Shanghai, China. Five months of observations from 1 May to 30 September 2018 showed that the air quality level is lightly polluted or worse (Ambient Air Quality Index, AQI, of > 100) for 12 d, of which ozone is the primary pollutant for 10 d, indicating ozone pollution was the main air quality challenge in Shanghai during summer of 2018. The levels of ozone and its precursors, as well as meteorological parameters, revealed the significant differences among different ozone levels, indicating that the high level of precursors is the precondition of ozone pollution, and strong radiation is an essential driving force. By increasing the input JNO2 value by 40 %, the simulated O3 level increased by 30 %–40 % correspondingly under the same level of precursors. The simulation results show that AOC, dominated by reactions involving OH radicals during the daytime, has a positive correlation with ozone levels. The reactions with non-methane volatile organic compounds (NMVOCs; 30 %–36 %), carbon monoxide (CO; 26 %–31 %) and nitrogen dioxide (NO2; 21 %–29 %) dominated the OH reactivity under different ozone levels in Shanghai. Among the NMVOCs, alkenes and oxygenated VOCs (OVOCs) played a key role in OH reactivity, defined as the inverse of the OH lifetime. A longer OH chain length was found in clean conditions primarily due to low NO2 in the atmosphere. The high level of radical precursors (e.g., O3, HONO and OVOCs) promotes the production and cycling of HOx, and the daytime HOx primary source shifted from HONO photolysis in the morning to O3 photolysis in the afternoon. For the sinks of radicals, the reaction with NO2 dominated radical termination during the morning rush hour, while the reactions of radical–radical also contributed to the sinks of HOx in the afternoon. Furthermore, the top four species contributing to ozone formation potential (OFP) were HCHO, toluene, ethylene and m/p-xylene. The concentration ratio (∼23 %) of these four species to total NMVOCs is not proportional to their contribution (∼55 %) to OFP, implying that controlling key VOC species emission is more effective than limiting the total concentration of VOC in preventing and controlling ozone pollution.
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Pike, R. C., J. D. Lee, P. J. Young, S. Moller, G. D. Carver, X. Yang, P. Misztal, et al. "Can a global model chemical mechanism reproduce NO, NO<sub>2</sub>, and O<sub>3</sub> measurements above a tropical rainforest?" Atmospheric Chemistry and Physics Discussions 9, no. 6 (December 21, 2009): 27611–48. http://dx.doi.org/10.5194/acpd-9-27611-2009.
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Abstract. A cross-platform field campaign, OP3, was conducted in the state of Sabah in Malaysian Borneo between April and July of 2008. Among the suite of observations recorded, the campaign included measurements of NOx and O3–crucial outputs of any model chemistry mechanism. We describe the measurements of these species made from both the ground site and aircraft. We examine the output from the global model p-TOMCAT at two resolutions for this location during the April campaign period. The models exhibit reasonable ability in capturing the NOx diurnal cycle, but ozone is overestimated. We use a box model containing the same chemical mechanism to explore the weaknesses in the global model and the ability of the simplified global model chemical mechanism to capture the chemistry at the rainforest site. We achieve a good fit to the data for all three species (NO, NO2, and O3), though the model is much more sensitive to changes in the treatment of physical processes than to changes in the chemical mechanism. Indeed, without some parameterization of the nighttime boundary layer-free troposphere mixing, a time dependent box model will not reproduce the observations. The final simulation uses this mixing parameterization for NO and NO2 but not O3, as determined by the vertical structure of each species, and matches the measurements well.
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Wolfe, G. M., J. Kaiser, T. F. Hanisco, F. N. Keutsch, J. A. de Gouw, J. B. Gilman, M. Graus, et al. "Formaldehyde production from isoprene oxidation across NO<sub><i>x</i></sub> regimes." Atmospheric Chemistry and Physics 16, no. 4 (March 2, 2016): 2597–610. http://dx.doi.org/10.5194/acp-16-2597-2016.
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Abstract. The chemical link between isoprene and formaldehyde (HCHO) is a strong, nonlinear function of NOx (i.e., NO + NO2). This relationship is a linchpin for top-down isoprene emission inventory verification from orbital HCHO column observations. It is also a benchmark for overall photochemical mechanism performance with regard to VOC oxidation. Using a comprehensive suite of airborne in situ observations over the southeast US, we quantify HCHO production across the urban–rural spectrum. Analysis of isoprene and its major first-generation oxidation products allows us to define both a "prompt" yield of HCHO (molecules of HCHO produced per molecule of freshly emitted isoprene) and the background HCHO mixing ratio (from oxidation of longer-lived hydrocarbons). Over the range of observed NOx values (roughly 0.1–2 ppbv), the prompt yield increases by a factor of 3 (from 0.3 to 0.9 ppbv ppbv−1), while background HCHO increases by a factor of 2 (from 1.6 to 3.3 ppbv). We apply the same method to evaluate the performance of both a global chemical transport model (AM3) and a measurement-constrained 0-D steady-state box model. Both models reproduce the NOx dependence of the prompt HCHO yield, illustrating that models with updated isoprene oxidation mechanisms can adequately capture the link between HCHO and recent isoprene emissions. On the other hand, both models underestimate background HCHO mixing ratios, suggesting missing HCHO precursors, inadequate representation of later-generation isoprene degradation and/or underestimated hydroxyl radical concentrations. Detailed process rates from the box model simulation demonstrate a 3-fold increase in HCHO production across the range of observed NOx values, driven by a 100 % increase in OH and a 40 % increase in branching of organic peroxy radical reactions to produce HCHO.